Multi-point box-end wrenches are well known in the art. The advantage of multi-point box-end wrenches is that these types of wrenches permit fasteners to pass clearly through. The disadvantage of such wrenches is that the retention of the box-end wrench upon a fastener is relatively difficult particularly when the box-end wrench is used in restricted locations where the fastener is not easily viewed when the user is attempting to rotate the wrench and fastener.
In an effort to overcome this deficiency there have been numerous attempts to provide a wrench structure that prevents the wrench head from slipping off or past the fastener with the subsequent risk of personal injury and/or damage to both the wrench and fastener as well as the consumption of the necessary time when using the wrench. See, for example, Canadian patent no. 1,257,487 and U.S. Pat. Nos. 2,774,259, 3,604,106 and 5,307,713.
The drawback of such structures is that although the wrench prevents the fastener from slipping through, there are situations in which it would be desirable to allow the fastener to pass therethrough. For example, when tightening two nuts together it may be necessary to have the wrench pass over the first fastener onto the second fastener. This is not possible using the structures disclosed in the aforementioned patents.
Other structures used for preventing the passage of a fastener there through incorporate the use of a single fixed projection or other type of structure for restricting passage of the fastener therethrough. See for example, Swedish patent no. 130,890 and U.S. Pat. No. 5,255,578. The drawbacks of these structures when engaged with the fasteners, is that the wrench has a tendency to cock and not properly engage the fastener.
Other structures have been proposed using a moveable projection for restricting the passage of the fastener therethrough. (See U.S. Pat. Nos. 2,697,371 and 2,751,802.) The disadvantage of such structures is that the movable portion is awkward to use.